1940s

Hallade’s apparatus, named after its inventor, the French engineer Emile Hallade, is a measuring instrument installed in railway carriages to detect and monitor track defects.

The apparatus is based on several pendulums that register the carriage's movements in height, lateral, and longitudinal directions. The pendulums control pens that write on a paper strip. To measure the largest possible movements, the apparatus was usually installed in the last carriage of the train.

On the different lines of the paper strip, one could read whether the track condition was good or bad. The strip was then used as a basis for the track workers who would address the problems.

Hallade’s apparatus served as a precursor to later generations of measurement vehicles, which record the same parameters but with higher precision.